testing raster monitors without the tube?

joemagiera

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Are there any tests that you can run on a color raster monitor without the tube to get any indication if the chassis is good? Specifically thinking about G07, 4600 & 4900's.
 
Yes, but it is not recommended for inexperienced monitor newbies, and it will only prove that the chassis powers up with high voltage. It will not show whether the colors, brightness, or sync are good.

You'd need an isolation transformer for power, a nice non-conductive surface, and some way to secure the anode cup so it can't shock you, the chassis, or anything else that is metal. Make sure the neckboard and chassis aren't touching. You can hook up power and see if you get a buzz on the anode, and measure the B+, but that's about it.

This is helpful for repairing chassis on a workbench in a way you can test voltages, but always be careful of the anode cup. Also, some chassis will not power up fully if the yoke isn't connected, some (like the K7000) need the dag wire connected if the anode cup is in a tube, and some won't power up without a video signal applied.

But the G07, 4600, and 4900 are not one of those. It's a lot harder to do this with a 4600, btw, but it is possible...
 
Not really. I mean, if you don't have a picture tube, you won't be able to see anything on the screen to see if it's working :) Also, it's not really a good idea to run a chassis without the flyback output connected to something - the HV will arc all over. If you pull the HOT, you won't get HV, but you won't be able to test much beyond the B+ supply. Also, most modern chassis probably won't even start without the proper yoke connected.

For working on TV's, I used to pull the horizontal output tube and run the chassis on the bench like that - no HV, but the tuner and sound would still work so you could troubleshoot the power supply and check voltages without having to reinstall the chassis in the (console) cabinet every time.

For arcade monitors though, you really do need a tube to troubleshoot and repair - there is very little you can do without one. Now, if you're trying to build a test station, you can probably just use a single tube (those are all the same), with no convergence rings, and just slide the appropriate yoke on. You will have horrible convergence and purity, but it should be good enough to verify that the chassis powers up, produces HV, has a stable B+ supply, syncs up properly, and drives all three guns.

-Ian
 
without the flyback output connected to something - the HV will arc all over.
-Ian

I often bench test with the anode cup out and secured, and there is no arcing as long as you have nothing metal within 4-5 inches. You just hear a faint buzz....
 
Also, some chassis will not power up fully if the yoke isn't connected, some (like the K7000) need the dag wire connected if the anode cup is in a tube, and some won't power up without a video signal applied.

But the G07, 4600, and 4900 are not one of those. It's a lot harder to do this with a 4600, btw, but it is possible...

OK, so you can run the older monitors without a yoke - I couldn't remember. I know that with TV's, the newer ones needed a yoke connected to start, but the older tube type and early solid state ones didn't care.

Pulling the HOT shuts down the HV supply, and allows for troubleshooting other things - but there aren't really any "other things" in an arcade monitor... BTW, a nice heavy glass jar works to put the anode cup into if you do leave the HOT in there.

Again, I can't recommend connecting a bare monitor chassis as any sort of useful troubleshooting technique, and it's dangerous to boot.

-Ian
 
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